Existing axial flow turbines such as Kaplan, Brauer (U.S. Pat. No. 1,065,208 6/1913), and propeller types have a specific range of pressures and fluid velocities which they can be efficiently operated in. Outside of this range these turbines will either become inefficient due to internal generation of turbulence, or cease to function because of the phenomenon known as cavitation. Such prior art axial flow turbines are unable to preclude cavitation because gradients in these turbines become too large when these turbines are operated outside their range. Further, present day turbo machine technology does not provide an axial flow turbine capable of transferring power between its rotor section and a gas while maintaining the static pressure of the gas, its density and temperature substantially constant.
Furthermore, an axial flow turbine as described by Johnson, U.S. Pat. No. 2,808,225 10/1957, does not contemplate a substantial reduction of the air axial and angular velocities. On the contrary, this turbine, as well as existing steam turbines, all work on the pressure drop and the corresponding expansion and acceleration of the gas as it moves along the length of their rotors. Due to its intended application as a high speed dental drill, the Johnson turbine does not consider efficiency as an important design criterion.